Synthesis
Methyl 4-amino-3-bromo-5-nitrobenzoate (10 g, 36.3 mmol) was used as starting material to form a suspension with tin(II) chloride (33 g, 14.5 mmol) in methanol (100 mL). The suspension was heated to 60 °C and maintained at this temperature for the reaction. Upon completion of the reaction, the reaction mixture was cooled to room temperature and subsequently concentrated to give a residue. The residue was adjusted to pH 11 with saturated aqueous sodium bicarbonate and the aqueous phase was extracted with dichloromethane (3 x 200 mL). The organic phases were combined, washed with saturated aqueous sodium chloride solution (200 mL) and dried with anhydrous sodium sulfate. Concentration of the organic phase afforded the target compound methyl 3,4-diamino-5-bromobenzoate as an off-white solid (5 g, 58% yield).1H NMR (CDCl3) data were as follows: δ 7.74 (s, 1H), 7.35 (s, 1H), 4.18 (wide s, 2H), 3.85 (s, 3H), 3.38-3.56 (wide s, 2H).
References
[1] Patent: US2011/111046, 2011, A1. Location in patent: Page/Page column 19
[2] Patent: WO2011/58473, 2011, A1. Location in patent: Page/Page column 39; 40
[3] Patent: WO2016/77378, 2016, A1. Location in patent: Page/Page column 111; 112
